saloon, few specimens of the less compound varieties of 
n*t7~Hist. agates, in which common calcedony, carnelian 
and heliotrope respectively form the predominant 
ingredients.-— Of flint, a weli known mineral 
substance, several interesting varieties are depo- 
sited in this case. 
(Case 8.) Contains principally opaline sub- 
stances, viz. specimens of the noble opal, which 
owes its beautiful play of colours to a multipli- 
city of imperceptible fissures in its interior; the 
Mexican sun or fire opal ; the common opal, 
a translucent white variety of which, appearing 
yellow or red when held between the eye and the 
light, is called girasol ; the semi-opal, agreeing in 
its principal characters with the common ; speci- 
mens of those varieties which, having the property 
of becoming transparent when immersed in water, 
are called hydrophanes,and vulgarly oculus mundi ; 
wood-opal or opalized wood ; j asp-opal, referred 
by some authors to Jasper ; the menilite, called 
also liver-opal, found at Menil-Montant, near 
Paris, in a bed of adhesive slate, a specimen of 
which is added. Some varieties of cacholong 
may likewise be referred to the opal-tribe. — The 
remainder of this case is occupied by the siliceous 
substance called horn- stone, divided into the con- 
choidal and splintery varieties ; the remarkable 
pseudomorphous crystals "from Sebneeberg, in 
Saxony, 
